I think re-using bubble mailers is fine. Fwiw, I don't ship many chips, but when I do, I re-use the bubble mailers. I do use clear packing tape to make sure the envelope is sealed up really good. Also, i would cover up the old addresses with labels that i have or covering up them up with the printout of the paypal address. The other thing I do is I keep the cardboard holders when you go to starbucks and put the chip in the cardboard and then put it in the bubble mailer, which is probably overkill, but seems to work pretty good as far as getting the envelope more rigid. Goodluck!